Biochemistry Exam 4

Where does the citric acid cycle take place in the cell?

Mitochondria

The activated carrier of acyl groups is

Coenzyme A

In the presence of oxygen, pyruvate is converted to

Acetyl CoA

This is a large, multi-subunit enzyme complex that links glycolysis and the citric acid cycle under aerobic conditions

Pyruvate dehydrogenase

This provides a flexible linker between active sites within the pyruvate dehydrogenase (PDH) complex

Lipoamide

Pyruvate is decarboxylated at this active site in PDH

E1

This coenzyme is the prosthetic group in the decarboxylation of pyruvate

Thiamine pyrophosphate

Arsenite inhibits the function of this component of the PDH

E3

This type of enzyme regulation process inhibits the PDH complex

Phosphorylation

This is caused by a deficiency in vitamin B1

Beriberi

In the reaction catalyzed by the PDH complex, the two carbons constituting the acetyl group are

Transferred to the lipoamide by an earlier intermediate in the process

The PDH complex is regulated by

Covalent modification, allosteric interactions, phosphorylation

This is not a product of the reaction catalyzes by PDH

Pyruvate

This is not a coenzyme necessary in the function of PDH

Biotin

The function of the citric acid cycle is to ___ high energy electrons

HarvestTh

The product formed by the condensation of oxaloacetate and acetyl CoA

Citrate

In the citric acid cycle, the ___ is produced by a substrate-level phosphorylation

GTP

How is phosphorylase b converted into phosphorylase a?

Through the addition of a phosphate to a serine residue

One mechanism for turning off glycogen degradation involves the removal of a phosphate group from glycogen phosphorylase by the enzyme ___

Protein phosphatase 1

Two critical hormones that signal for glycogen breakdown are

Glucagon and epinepherine

What physiological conditions render phosphorylase b less active?

High ATP and high glucose 6-phosphate levels

The transferase enzyme shifts a block of ___ glycolyl units

Three

Which molecules must be excluded from the active site of glycogen phosphorylase?

Water

What is the function of liver glycogen degradation?

To export glucose to other tissues when glucose levels are low

Conversion of glucose 1-phosphate to glucose 6-phosphate is carried out by the enzyme

Phosphoglucomutase

Calcium binds and leads to the activation of which enzyme in glycogen degradation?

Phosphorylase kinase

What is the chemical effect of rotenone on aerobic metabolism?

The flow of electrons from NADH to CoQ is blocked

Acceptor control of oxidative phosphorylation means that the rate of respiration depends upon the level of ___

ADP

What type of gradient is critical to ATP formation by oxidative phosphorylation?

Proton

What is the reaction of ATP synthase?

ADP3- + HPO4 2- + H+ > ATP 4- + H2O

A diet pill that acts to increase oxygen consumption during electron transport without ATP production is likely what kind of compound?

An uncoupler

When glucose is totally oxidized to CO2 and H2O how many ATP molecules are made by oxidative phosphorylation out of a maximum yield of how many ATP molecules?

26 out of 30

What are the driving force (energetic) costs for the ATP-ADP translocase?

Membrane potential from electron transport

The subunit of the ATPase embedded in the inner mitochondrial membrane is the:

F0 subunit

What occurs after a carbohydrate-rich meal?

Blood-glucose levels increase leading to glycogen storage in the liver

During a period of exercise, which enzymes will dominate in muscle?

Glycogen synthase b

What enzymes are required to synthesize a 1,4-glycosidic bonds in glycogen?

Glycogen synthase

Glycogen breakdown and synthesis are said to be reciprocally regulated. This means that

The same effectors affect both processes but in opposite directions

In order for regulation of glycogen metabolism to function, there must also be a means to reverse the regulatory effects of the various kinases. Reversal of kinase activation is accomplished by protein phosphatase 1, an enzyme which

Hydrolyzes the phosphate from the modified enzyme

Glycogen synthesis adds glucose units to growing glycogen molecules using

UDP glucoseT

he attachment of glucose to UDP is a readily reversible reaction. What provides the driving force in favor of the synthesis of UDP-glucose?

The energy from the subsequent hydrolysis of the pyrophosphate

Glycogen breakdown can be regulated hormonally when ___ is secreted from the ___

Glucagon, pancreas OR Epinephrine, adrenal medulla

The glycogen phosphorylase enzyme carries out a phosphorolysis reaction resulting in the formation of

Glucose-1-phosphate

Most of the glucose residues in glycogen are linked by this type of bond

alpha-1,4-glycosidic

This is the glycogen unit where interconversion between the open and closed conformation of the anomeric carbon is possible

The reducing end

The process by which a bond is cleaved by the addition of orthophosphate is

Phosphoroylsis

The type of bond that is located at the branch points in glycogen is

alpha-1,6-glycosidic

This is the liver enzyme that cleaves the phosphate from glucose-6-phosphate

Glucose 6 phosphatase

This enzyme catalyzes the phosphorylation of glycogen phosphorylase

Phosphorylase kinase

This protein is the gamma subunit of phosphorylase kinase

Calmodulin

This hormone signifies a starved state

Glucagon

This takes place instead of hydrolysis in glycogen breakdown

Phosphorolysis

This enzyme serves as the glucose sensor enzyme in liver cells

Phosphorylase a

The fact that liver tissue contains glucose-6-phosphatase while muscle tissue does not is physiologically important because

One of the major functions of the liver is to maintain the blood glucose level

Synthesis of glycogen starts with the phosphate group transfer from UTP to

Glucose

This is the activated form of glucose that is required for glycogen synthesis

UDP glucose

Hydrolysis of __ drives the formation of UDP glucose

PPi

Glucosyl units are added to the ___ end, or terminal of glycogen

Nonreducing

This is the key regulatory enzyme in glycogen synthesis

Glycogen synthase

Glycogen ___ is inhibited by phosphorylase kinase

synthesis

This dissociates from phosphorylase a in the T state

PP1

This is the storage disease in which light exercise results in cramps

McArdle disease

The protein ___ serves as the primer used by glycogen synthase

Glycogenin

This is the glycogen storage disease in which the defective enzyme is glucose 6-phosphatase

Von Gierke disease

What are the reactive oxygen species and why are they dangerous to cells?

OH, H2O2, O2-, O2 2-
These react easily with proteins, lipids, and nucleic acids

Compare fermentation and respiration with respect to electron donors and acceptors.

In fermentation, an organic molecule is both the electron donor and acceptor.
In respiration, an organic molecule is the electron donor but oxygen is the electron acceptor.

This is where oxidative phosphorylation occurs in eukaryotes

Mitochondria

This is an ATP generating process in which an inorganic substance such as oxygen serves as the ultimate electron acceptor

Respiration

The permeability of the outer mitochondrial membrane is primarily due to the presence of

Porins

This electron carrier is a derivative of quinone and has an isoprenoid tail

Coenzyme Q

This enzyme catalyzes the reduction of O2

Cytochrome c oxidase

This prosthetic group is present in complexes 1, 2, and 3 of electron transport

Iron-sulfur clusters

This citric acid cycle enzyme is also part of an electron transport complex

Succinate dehydrogenase

This is the prosthetic group in complex 1 that accepts electrons from NADH

Flavin mononulceotide (FMN)

This is the complex with three Fe-sulfhydryl electron acceptors

Complex 2

This is the process by which cytoplasmic NADH can be oxidized by O2 using the ETC

Respiration

Which electron transport complex associated with the inner mitochondrial membrane is not involved in the generation of a proton gradient?

Succinate-q reductase (complex 2)

What describes the direction of proton movement relative to electron transfer and phosphorylation?

Electron transfer pumps protons out of the matrix. As the protons reenter through ATP synthase, ATP is produced in the matrix

What points to the endosymbiotic event yielding intracellular mitochondria?

The have specific transcription and translation machinery, they have a double membrane, they contain their own circular DNA

The path taken by electrons to water from NADH generated during the citric acid cycle will not pass through

FAD

The process of glycolysis occurs in the cytoplasm. The electrons from the NADH generated during glycolysis

Enter the mitochondrial electron chain directly as NADH freely enters the mitochondria

ATP synthase

Converts the proton motive force into ATP

The proton-motive force

Is composed of a chemical gradient and a charge gradient

The ETC

Generates the proton gradient

The Glycerol-3-phosphate shuttle

Transfers cytoplasmic NADH to mitochondrial FADH2

The Malate-aspatate shuttle

Transfers cytoplasmic NADH to mitochondrial NADH

Respiratory (acceptor) controll

ADP controls the rate of respiration

Uncoupling proteins

Result in heat instead of ATP

The F1 subunit

Is a catalytic unit

The F0 subunit

Is a proton channel

The c ring

Is a proton merry-go-round

The presence of uncoupling proteins allows ___ energy from the mitochondrial ETC to be used for ATP synthesis and __ for the production of heat

Less, more

The energy generation of ATP using ATP synthase can be thought of as the reverse of what chemical reaction?

ATP hydrolysis and proton movement against a gradient

Peter Mitchell proposed the ___ hypothesis that describes how ___ and ___ are coupled.

Chemiosmosis, electron transport, membrane potential

The four components of the ETC can be inhibited by different compounds. What is a correct match of an electron transport chain complex with its inhibitors?

Cytochrome c oxidase and N3-

The entry of ADP into the mitochondria is coupled with the exit of __ and is carried out by ___

ATP, ATP-ADP translocase

In brown fat ___ is responsible for ___oxidative phosphorylation and ATP synthesis

Thermogenin, uncoupling

What is the mechanistic basis for the observation that inhibitors of ATP synthase also lead to an inhibition of the ETC?

ATP synthase inhibitors respond to the influx of protons into the mitochondria as ATP is generated. This ensures that as ATP is produced, the proton gradient does not grow so large outside the mitochondria that the ETC cannot pump protons against the gradient

Which conditions activate PDH kinase, which catalyzes the phosphorylation and inactivation of E1 in the PDH complex?

Elevated concentrations of NADH and ATP

Pyruvate dehydrogenase is ___ when ATP-ADP ratios are high

Inhibited